154 PBINCIPLES OF PLANT CULTURE 



sun-scald (185). Smearing the stems with blood has 

 also been recommended. 



274. Woodchucks are often troublesome to growing 

 crops, but as they are seldom numerous, shooting or 

 trapping generally suffices to prevent serious damage. 

 Moles are very troublesome in some localities by eating 

 the roots of plants. They may be largely controlled by 

 the use of mole-traps. Pouring a little carbon bisulfid 

 into their holes is also generally effective. 



275. Birds are often troublesome by eating unhar- 

 vested fruits and seeds. Inclosing the trees or plants 



with fish netting, when 

 this is practicable, is 

 perhaps the most satis- 

 factory preventive. The 



Fig. 67. — Screen-covered frame, for pro- netting is not expensive, 

 tecting hills of the melon and cucum- , , , 



ber. and the same piece may 



be used several seasons. 



276. Useful insects. — Many insects are beneficial by 

 destroying harmful insects or by promoting pollination 

 (150). We should not, therefore, wage , indiscriminate 

 warfare upon all insects. 



277. Preventive methods. — Methods of preventing 

 insect ravages to plants are various, as inclosing the plants, 

 trapping, repelling or removing the insects, destroying 

 them by means of insecticides, or preventing reproduc- 

 tion by destroying the eggs. The important question in 

 the case of any injurious insect is by which one of these 

 methods it may be most effectually and cheaply con- 

 trolled. 



278. Inclosing the plants is practicable in a few cases, 

 as with the striped cucumber beetle (Diabrotica vit- 

 tata). The hills in which cucumbers, melons, squashes 



